As noted in the above-cited patents, one of the previous advances in the plastics industry was the development of polyurethane foams which are cellular plastic materials generally formed by the reaction of long chain polyol compounds and organic polyisocyanates. Cellular plastics are available in various degrees of rigidity, ranging from soft, flexible foams useful in cushioning, clothing interliners, rug underlays, sponges and bath mats; semi-rigid foams, useful particularly as crash pads; and rigid foams for structural and insulation purposes. The final properties of the urethane foams depend principally on the choice of polyethers, polyesters or other long chain polyhydroxyl compounds which are converted by the polyisocyanate into a high molecular weight polymer which is then foamed by a suitable foaming system, usually a reaction of water with the free isocyanate content of the polymer, resulting in the formation of carbon dioxide which expands the resin into the desired cellular plastic. The control of branching in the reactants permits an extremely wide range of properties in the final foamed plastic. The density of the foam is controlled to a great extent by the amount of water employed. The configuration of the cell depends principally on the equivalent weight of the long chain polyhydroxyl materials favoring the production of a closed cell structure and the higher equivalent weight polyhydroxyl materials leading to the open-cell structure. The degree of branching of the polyhydroxyl reactant also influences the cell character.
The flexible and semi-rigid foams are processed for the aforementioned applications in a manner such that the foam has a low density, usually from about 1.25 to 4 pounds per cubic foot, and preferably as low a density as is consistent with the provision of a product of adequate strength, etc. Moreover, such flexible and semi-rigid foams should have an open-celled structure for most applications, which is to say that essentially all (i.e., at least about 90 percent), of the cells are intercommunicating since such a foam configuration is essential to the realization of acceptable foams for cushioning, clothing interliners, crash pads or the like. Rigid foams, in contradistinction, may have varying density values ranging up to 30 pounds per cubic foot or higher and usually have a closed cell structure.
For various applications, however, it is often desired to utilize polymer materials other than polyurethanes, to obtain performance characteristics not provided by or obtainable from polyurethane itself. Unfortunately, however, many other polymer systems do not lend themselves readily to being formed into open cell, resilient structures. Silicone polymers are highly desirable for use as products that will come into contact with the human body, as silicone is substantially inert or non-reactive with the skin. In the health care market, such products would be desirable for paddings for beds or other pieces of furniture, and other resilient products that are designed to come into contact with the body. Silicone polymers are not readily susceptible of being formed into open-cell resilient structures, such as sheets of foamed material.
It would be desirable, therefore, if an apparatus and method could be provided that would produce a foam product that is ignition resistant or flame retardant. It would also be desirable if such an apparatus and method could be provided that would produce a foam product that is resistant to bacteria, fungus and mold and is anti-microbial. It would be further desirable if such an apparatus and method could be provided that would produce a foam product that is resistant to environmental and physical degradation. It would be still further desirable if such an apparatus and method could be provided that would produce a foam product that is relatively light weight. It would also be desirable if such an apparatus and method could be provided that would produce a foam product that is relatively dense and open-celled or breathable. It would be further desirable if such an apparatus and method could be provided that would produce a foam product that is washable.